Metal working operations performed on a round metal bar are commonly carried out through the use of a lathe and cutting tools associated therewith. The bar is gripped by the collet chuck of the lathe to extend therefrom, and the bar is rotated about its axis while various cutting tools are serially applied to the rotating extending end of the bar to perform multiple cutting operations on the bar, such cutting tools being carried in a cross slide square turret or the like in a manner which permits the plurality of tools to be separately and selectively disposed at a cutting disposition with respect to the rotating bar. The last operation performed is commonly that of cutting off the extending end portion of the workpiece which has been lathe-cut in the previous operations to a desirable shape, and such cutting off is commonly done with a narrow cutting tool having a straight cutting edge which is advanced radially into the workpiece, cutting an annular groove therein until the remaining metal beneath the groove becomes so weak that the extending end portion beyond the groove breaks off from the chucked main body of the round bar or workpiece.
Since tool locations on the conventional cross slide square turret of a lathe are limited in number, the cutoff tool is sometimes mounted on the rear end of the cross slide at the back of the lathe to cut upside-down as compared with other tools mounted in the cross slide turret. Since it is desirable in many cases to chamfer or bevel the sharp peripheral edges of the cutoff portion, such chamfering may be done by a separate chamfering tool which cuts a V-groove of suitable depth in the workpiece at the cutoff location prior to cutting off, or alternatively, the cutting off might be stopped part way through the workpiece while the edges are chamfered with a separate tool. In all the above cases, valuable lathe time and labor is used by performing the chamfering as a separate operation from the cutting off.
By substantial contrast, the tool holder of the present invention permits the chamfering operation to be accomplished simultaneously with the cutting off, thereby saving lathe time, as well as eliminating the possibility of accidental omission of the chamfering operation, as sometimes happens when a lathe operator is depended upon to chamfer as a separate operation.